One method for calculating the amount of mass flow of exhaust gas recirculation (EGR) in a diesel engine is to measure the differential pressure across a mechanical device. Certain of these devices will generate a differential pressure that is proportional to the volumetric flow (in volume per unit of time), such as a verturi. By measuring the temperature and pressure of this flow, this volumetric flow can be converted to a mass flow. An EGR differential pressure sensor (EGR DPS) has been designed to this purpose. This is a sensor that measures the differential pressure across this device and provides a voltage signal that is proportional to this pressure.
Due to the extreme environment created by heavy duty diesel engine EGR, output drift can be a problem with the EGR DPS. Output drift is the situation where the output of the sensor deviates from its calibrated value. Often the drift over the entire sensor calibration range can be tracked by recording the amount of sensor error with no pressure applied. In addition, if this error is large enough it can be determined that the sensor is defective.
1. Field of the Invention
The present invention relates to a method to auto calibrate an exhaust gas recirculation differential pressure sensor to correct for sensor output drift.
2. Description of the Related Art
A method for controlling an internal combustion engine having a variable geometry turbocharger (VGT) and an exhaust gas recirculation (EGR) system in the face of sensor failures and mechanical faults includes generating accurate substitute values for use by the engine control logic when EGR and VGT system-related sensors are diagnosed as having failed during operation, and maintaining controlled performance of the VGT system in the face of sensor failures or mechanical faults associated with the EGR or VGT system.
A closed-loop actuator control system includes a single PI controller for controlling one or more actuators to minimize an error between an engine operating parameter value and a reference parameter value. In multiple actuator systems, the control system of the present invention is operable to drive one actuator to its upper limit before transferring control to the next actuator. The proportional gain block of the PI controller preferably includes a bumpless gain feature operable to limit the rate of change of the proportional gain to thereby provide smooth gain scheduling. A feed forward block may optionally be included that preferably includes the bumpless gain feature. The actuator control system further includes anti-windup logic operable to disable the PI integrator if the actuator drive signal is upper or lower limit bounded and the error signal is greater or less than zero respectively, thereby creating dynamic saturation of the PI integrator.
A system for estimating turbocharger compressor outlet temperature includes an engine controller responsive to any two of corrected turbocharger speed, corrected fresh mass air flow and turbocharger compressor pressure ratio (compressor outlet pressure/compressor inlet pressure) to compute compressor outlet temperature based on a corresponding compressor outlet temperature model.
An exhaust gas recirculation (EGR) system for an engine with a variable geometry turbocharger (18) incorporates a master rotary electric actuator (REA) (50) with a microprocessor controller (53) receiving condition signals (46, 48a-e) from sensors (48) associated with the turbocharger and the engine control unit (ECU) (54) and positioning the turbine inlet nozzle (44) geometry of the turbocharger in response to a predetermined matrix of the condition signals. A slave REA (52) is connected through an internal processing unit (58) to the controller to position an EGR valve (34). The processing unit provides an actual position signal to the controller which responds with a desired position signal based on the predetermined condition signal matrix. The processing unit engages the slave REA to position the EGR valve.